Free 'health camps' for poor people in India have grown popular, Frederik Joelving, a journalist based in Denmark wrote in the journal.
Local residents are invited to the camps that may include medical testing done by drug representatives or technicians, he said.
The researchers have evidence that unlicensed employees from several Indian drug firms and from the Indian arms of Abbott, Bayer, GlaxoSmithKline, Roche, and Sanofi have tested patients at health camps.
Likewise, for doctors to prescribe specific products in return for testing services from a drug company is not only 'totally unethical,' it also violates MCI regulations, said K L Sharma, joint secretary at the Ministry of Health and Family Welfare.
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Cipla acknowledged that its employees test patients, said Joelving. A Roche spokesperson said that Roche Diabetes Care India donates testing supplies to diabetes education camps but added that "people with diabetes who attend the camp test on their own, after having signed a written consent."
However, Pinaki Dutt, a GSK sales representative from West Bengal told Joelving in 2013 that he and his colleagues were required by 'company policy' to do blood sugar tests at health camps.
The Indian subsidiaries of Abbott Laboratories have been particularly active in the push for screening, claimed Joelving, with each of the company's business divisions organising health camps.
"Health camps must not be supported in exchange for an explicit or implicit understanding to purchase, order, recommend, prescribe or provide favourable treatment to any Abbott products," Abbott officials told The BMJ.
However, an Abbott representative who does screening at diabetes camps said that these services have nothing to do with charity.
"The only objective is the business transaction," said the representative, who spoke on condition of anonymity.